Nonferrous alloy



Patented Mar. 30, 1948 g V assa es "NoNFERRoUsALLov 4,031 in, Burbank, Calif., assig-rior of c'kheed Aircraft corporation,

N Drawing. Application January 2, 1945, Serial No. 571,113

3 Claims. (01. 75 -16'6) This invention relates to a non-ferrous, moderate melting temperature alloy which is substantially non-shrinking in character, has good casting properties and adequate strength and hardness to form dies and punches for drop hammers and presses.

The alloy of this invention eliminates the use of scarce, critical and/or high priced ingredients,

such as cadmium, bismuth, mercury and tin, and is therefore currently available as well as being much cheaper than prior alloys for these purposes which call for such critical components.

It is an object of this invention to produce an improved and less expensive and more available alloy of a type suitable for casting dies and punches for use in drop hammers and presses working on the shaping and/or drawing of sheet metal wherein the volume of production does not justify the use of expensive machined steel dies. In metal aircraft production, for example, a great many individual punches and dies are required that would be prohibitively costly if made in steel to pre-war automobile standards. It has h'eretofore been proposed to use quaternary non-ferrous alloys for such dies and/or punches. Such quaternary alloys commonly require bismuth,-

cadmium, tin and/or mercury, most of which are either expensive and/or critical supply items under present conditions.

I have found that a binary alloy of lead and antimony, tempered with a small amount of copper or tin, produces a satisfactory die and/or punch alloy having adequate hardness to form sheet metal parts and which can be cast to shape in suitable plaster or sand molds, as the shrinkage in cooling can be controlled within narrow limits by the antimony content, and/or mold cooling arrangements for heavy sections of the die.

As examples of a suitable alloy formula for casting drop hammer dies, I prefer to use 26% to 28% of antimony and to copper or tin, the balance, aside from normal impurities in the elements, being lead, This formula may be varied within the ranges of 25% to 30% antimony, 69% to 75% lead, and 0 to 1% copper or tin, again ignoring impurities in the commercially available elements. As an all around material suitable for uses including dies, anchor or matrix material, drill bushings for jigs, and the like, I hold the composition to 26% to 27% antimony,

V /2 copper and the balance lead.

In forming punches and dies it is desirable to have the punch slightly softer than the die and/or to have the punch soften at a lower temperature,

itwenab'le' the punch' to-be p ed or f'ca into the die, and to-enable'thepunch 'to yield relative to the die to complete the forming operation on the sheet metal part being worked on. To this end Lmay vary the allot formula for the punch to consist of antimony 18% to 20%, copper /8% to and the balance lead, ignoring normal impurities in the commercially available elements.

In compounding th'ese alloys, I have found that the antimony content controls both the shrinkage and hardness; under 25% being softer and increasing the shrinkage, while over proves too brittle for satisfactory use as a die material subject to impact as in drop hammers. The copper greatly improves the casting qualities and reduces the hand finishing time on dies, but may be omitted when the alloy is used for drill bushings and/or for locating or anchoring supports, piercing punches, locating pins or other uses where surface finishing or condition does not affect the use of the material. The amount of copper that can be added is determined by the quality of the lead and the shrinkage allowed. With the commercial grade called corroding lead, 1% copper is permissible, while with so-called caulking lead, over 4% copper causes excessive shrinkage. A grade of lead called antimonal lead can be used, which carries from 1 to 8% antimony, so that with this grade of lead, proper allowance for the antimony content thereof must be made in the foregoing examples,

The melting point of my improved alloy will vary from 450 to 500 Fahrenheit, depending chiefly on the copper content; and the shrinkage will vary from nothing to /1000 of an inch per foot according to the section of the casting. I have found that the increased shrinkage of thick dies can be overcome by rapid cooling, as by casting hollow inserts and/or cores therein, as the shrinkage appears to be due to the annealing effect of a long and slow cooling period.

While I have specified small amounts of copper as the tempering agent, I have found that tin will serve my purpose. Copper is both cheaper and more plentiful than tin, and tends to raise the melting point of the alloy, while tin lowers the melting point. a melting point differential between a punch and die can be obtained by using copper in the die alloy and tin in the punch alloy.

Having thus described my invention and the present preferred embodiments thereof, I desire to emphasize the fact that many modifications may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim as my invention:

1. A punch and die alloy of th'e class described consisting of antimony 25% to 30%, copper from a trace to 1%, and the balance lead.

2. A predominately lead die alloy consisting of one part of antimony combined with from two and one-half to four parts of lead, together with an appreciable amount less than 1% copper.

3. A lead base punch and die alloy consisting of 26% to 28% antimony and%% to cop- 10 per and the balance lead.

CLARENCE 0. PREST.

REFERENCES CITED The following references are of record in the 1 file of this patent:

UNITED STATES PATENTS Number Name Date 1,029,152 Tibbetts L- June 11, 1912 1,203,991 Dwyer NOV. 7, 1916 1,691,932 Muller NOV. 20, 1928 FOREIGN PATENTS Number Country Date 696,724 France Oct. 20, 1930 5 OTHER REFERENCES 

